Lower Life Cycle Greenhouse Gas Emissions Research Articles

Efficient Depolymerization of Poly(ethylene 2,5-furanoate) Using Polyester Hydrolases.

Poly(ethylene 2,5-furanoate) (PEF) is considered to be the next-generation green polyester and is hailed as a rising star among novel plastics. It is biobased, is nontoxic, and has comparable or improved properties compared to polyethylene terephthalate (PET). Biobased PEF offers lower life-cycle greenhouse gas emissions than PET. However, with its industrial production starting soon, relatively little is known about its actual recyclability. This work reports on the near complete depolymerization of PEF using two efficient PET hydrolases, FastPETase and leaf compost-cutinase (LCC), at loadings 4.5-17 times lower than previously reported. FastPETase and LCC exhibited maximum depolymerization of PEF, measured by weight loss and 2,5-furandicarboxylic acid (FDCA) production, using potassium phosphate-NaOH buffer at 50 and 65 °C, respectively. The 98% depolymerization of 13 g L-1 PEF film was achieved by three additions of the LCC in 72 h, while 78% weight loss was obtained using FastPETase in controlled conditions. Nonetheless, 92% weight loss was obtained with FastPETase when using only 6 g L-1 PEF. The main reaction products were identified as FDCA, ethylene glycol, and mono(2-hydroxyethyl)-furanoate. LCC performed better than FastPETase, in terms of both FDCA release and weight loss. The effect of crystallinity was evident on the enzymes' performance, as only 4% to 7% weight loss of crystalline PEF (32%) was recorded. Microscopy studies of the treated PEF films provided information on the surface erosion processes and revealed higher resistance of the crystalline phase, explaining the low level of depolymerization. The study presents important insights into the enzymatic hydrolysis of biobased PEF material and paves the path toward more viable applications within biopolymer waste recycling.

Analyzing the impact of geographic variability on emissions reduction and cost efficiency in automotive lightweighting strategies

Lightweight design is crucial in automotive design, especially for battery electric vehicles (BEVs), as it can extend driving range or minimize battery size for a set distance. However, the choice of materials like high-strength steels, while beneficial for vehicle weight, often carries greater environmental costs during production. A comprehensive analysis considering the entire lifecycle and electricity sources is essential to identify truly eco-friendly materials. The market introduction of innovative materials like green steel and recycled products further complicates the selection process due to increased competition. Current assessments of lightweight strategies are complex and challenging to compare, highlighting a research gap in easy-to-understand and actionable evaluations. This study aims to investigate automotive lightweighting across various propulsion systems and regions using prospective Life Cycle Assessment (LCA). It introduces a novel approach by examining how the mix of electricity generation affects the environmental benefits of lightweight materials. A new Key Performance Indicator (KPI) is proposed to help those with limited LCA expertise evaluate the environmental impact of different structural materials. The research also provides visual tools and analyzes cost savings from lower lifecycle greenhouse gas emissions, presenting a rounded view of the economic and environmental advantages of diverse lightweight strategies.

In-Depth Lifecycle Assessment of Ballasted Railway Track and Slab Track Considering Varying Subsoil Conditions

This study assesses and compares lifecycle (LC) greenhouse gas (GHG) emissions from the two main railway track construction types: ballasted track and slab track. In this study, preexisting soil conditions are considered, as they significantly influence necessary measures during the construction phase for each type. This study is executed for Austrian boundary conditions with speeds up to 250 km/h. The results show that ballasted track is associated with 11–20% lower LC GHG emissions, whereby the variation in relative emission reduction is associated with additional soil reinforcement treatments due to varying preexisting soil conditions. Poor preexisting soil conditions increase LC GHG emissions by 26%, underlying the necessity to integrate this parameter into the lifecycle assessment of railway track. In contrast to the higher service life of slab track construction, this type amounts to higher masses of concrete and demands more extensive measures for soil enhancement due to the higher stiffness of the track panel. Only in tunnel areas does slab track cause lower GHG emissions since soil reinforcements are not necessary due to an existing concrete base layer after tunnel construction. For both construction types, over 80% of the GHG emissions stem from material production. Hence, circular economy as well as innovations within steel and concrete production processes hold significant potential for reducing GHG emissions.

ALTERNATE FUEL BIODIESEL

The rapid growth of industrialization and transportation has led to a significant increase in greenhouse gas emissions and environmental degradation. To mitigate these challenges, there is an urgent need for sustainable energy solutions that can reduce dependence on fossil fuels and minimize environmental impact. Bio-diesel, a renewable and cleaner-burning fuel derived from organic sources, has emerged as a promising alternative to traditional petroleum-based diesel. This abstract provides an overview of bio-diesel, its production process, properties, and its environmental benefits. Bio-diesel is typically produced from feedstocks such as vegetable oils, animal fats, and waste cooking oils through a transesterification process that converts triglycerides into esters. The resulting bio-diesel exhibits similar properties to petroleum diesel, making it compatible with existing diesel engines and infrastructure. One of the significant advantages of bio-diesel is its reduced carbon footprint. It has a significantly lower lifecycle greenhouse gas emissions compared to petroleum diesel, primarily due to the absorption of carbon dioxide during the growth of the feedstock plants. Bio-diesel also contributes to a reduction in air pollutants, such as sulfur oxides and particulate matter, resulting in improved air quality and human health benefits. Additionally, bio-diesel offers economic benefits by promoting local agriculture and creating new job opportunities in the biofuel industry. The utilization of waste cooking oils and animal fats as feedstocks also contributes to waste reduction and efficient resource utilization. Despite its numerous benefits, challenges remain in the widespread adoption of bio-diesel. These challenges include feedstock availability, land use competition with food production, and the need for consistent quality standards. Ongoing research and development efforts are focused on optimizing the production process, exploring alternative feedstocks, and improving the overall sustainability of bio-diesel production. In conclusion, bio-diesel holds great potential as a sustainable alternative to petroleum diesel, offering environmental, economic, and societal benefits. Its reduced carbon footprint and compatibility with existing infrastructure make it a viable option for transitioning towards a greener future. Further advancements in technology and policies supporting bio-diesel production and utilization will play a crucial role in realizing its full potential and achieving a more sustainable energy landscape

Proposal of Zero-Emission Tug in South Korea Using Fuel Cell/Energy Storage System: Economic and Environmental Long-Term Impacts

This study presents the results of economic and environmental analysis for two types of zero-emission ships (ZESs) that are receiving more attention to meet strengthened environmental regulations. One of the two types of ZES is the ZES using only the energy storage system (All-ESS), and the other is the ZES with fuel cell and ESS hybrid system (FC–ESS). The target ship is a tug operating in South Korea, and the main parameters are based on the specific circumstances of South Korea. The optimal capacity of the ESS for each proposed system is determined using an optimization tool. The total cost for a ship’s lifetime is calculated using economic analysis. The greenhouse gas (GHG) emission for the fuel’s lifecycle (well-to-wake) is calculated using environmental analysis. The results reveal that the proposed ZESs are 1.7–3.4 times more expensive than the conventional marine gas oil (MGO)-fueled ship; however, it could be reduced by 1.3–2.4 times if the carbon price is considered. The proposed ZESs have 58.7–74.3% lower lifecycle GHG emissions than the one from the conventional ship. The results also highlight that the electricity- or hydrogen-based ZESs should reduce GHG emissions from the upstream phase (well-to-tank) to realize genuine ZESs.

Comparative life cycle assessment of a reinforced concrete residential building with equivalent cross laminated timber alternatives in China

With the development of mass timber, cross laminated timber (CLT) has gradually become a sustainable alternative to conventional building materials to alleviate the increasing energy consumption and carbon emissions by the building sector. This study aims to explore the life cycle greenhouse gas emissions (LCGHGE) and life cycle primary energy (LCPE) of three high-rise residential buildings in the cold region of China through a life cycle assessment approach. The three buildings are conventional reinforced concrete (RC), CLT and hybrid CLT buildings. The results show that CLT and hybrid CLT buildings produce 15.00% and 10.77% lower LCGHGE, respectively, compared to the RC building within a 50-year service life. A clear difference in greenhouse gas (GHG) emissions and primary energy (PE) in the product and construction stages is visible, with 46.52% and 37.24% of embodied GHG emissions reduced in CLT and hybrid CLT buildings, respectively, compared to the RC building. In the operational stage, RC building has lower PE and GHG emissions to CLT alternatives. The thermal mass effect has led to a 2.25% and 2.12% PE increase for space heating and cooling in CLT and hybrid CLT buildings, respectively, compared to the RC building. For the End-of-Life (EoL) stage, CLT demonstrates great recycling potential and biomass residues. The sensitivity analysis shows that the design of the low U-value of the building envelope and high-efficiency energy systems has a significant relationship with energy reduction during the operational phase of the three buildings, magnifying the impacts of the initial and EoL stages. • CLT and hybrid CLT buildings produce 15.00% and 10.77% less LCGHGE than RC buildings in Tianjin, China, respectively. • Mass timber construction shows great advantages over RC buildings in the P&C/EoL stage. • The operational GHG emissions and PE of CLT and hybrid CLT buildings were 12–13% higher than those of the RC building. • Energy-efficient methods can enhance the LCA performance of hybrid CLT building.

Assessment of the greenhouse gas emission footprint of a biorefinery over its life cycle

Expanding the product portfolio of a biorefinery has the potential to improve the economics of the biorefinery as it not only increases revenue but also improves valuable feedstock use. Such process improvement, however, results in added complexity, energy consumption, and emissions. This study evaluated the energy consumption and greenhouse gas (GHG) emissions of an integrated multi-product biorefinery from a life cycle perspective. Six pathways were assessed in which the by-products of fast pyrolysis – biochar and non-condensable gases (NCGs) – were upgraded to produce ethanol and hydrogen, in addition to bio-oil. The six pathways include six corresponding biorefinery configurations. The configurations differ by NCG application and the kind of fuel used to supplement process heat demand. The GHG emissions intensity of the assessed pathways is between 13.54 and 43.13 gCO2eq/MJ. Our assessment shows a higher GHG emissions intensity in the assessed pathways than the base pathway, in which only bio-oil is produced. Generally, the emission intensities of biorefinery products are lower than when these products are produced from fossil sources but higher than when produced from dedicated bioenergy technologies. Also, when the products are put into an end-use application, like power generation, bio-oil shows lower life cycle GHG emissions compared to conventional fossil-based power plants. When the transportation of the products to the power plant is considered, the life cycle GHG emissions of hydrogen are higher than from the conventional generation methods. Sensitivity analyses show that reducing the feedstock moisture content and increasing ethanol titer can provide significant emission reduction potential. Outside the boundaries of the biorefineries, feedstock transportation also has an impact on the overall emissions.

Regionalized Life Cycle Greenhouse Gas Emissions of Forest Biomass Use for Electricity Generation in the United States.

This study presents a cradle-to-grave life cycle analysis (LCA) of the greenhouse gas (GHG) emissions of the electricity generated from forest biomass in different regions of the United States (U.S.), taking into consideration regional variations in biomass availabilities and logistics. The regional biomass supply for a 20 MW bioelectricity facility is estimated using the Land Use and Resource Allocation (LURA) model. Results from LURA and data on regional forest management, harvesting, and processing are incorporated into the GHGs, Regulated Emissions, and Energy Use in Technologies (GREET) model for LCA. The results suggest that GHG emissions of mill residues-based pathways can be 15-52% lower than those of pulpwood-based pathways, with logging residues falling in between. Nonetheless, our analysis suggests that screening bioenergy projects on specific feedstock types alone is not sufficient because GHG emissions of a pulpwood-based pathway in one state can be lower than those of a mill residue-based pathway in another state. Furthermore, the available biomass supply often consists of several woody feedstocks, and its composition is region-dependent. Forest biomass-derived electricity is associated with 86-93% lower life-cycle GHG emissions than the emissions of the average grid electricity in the U.S. Key factors driving bioelectricity GHG emissions include electricity generation efficiency, transportation distance, and energy use for biomass harvesting and processing.

Regional variation of greenhouse gas mitigation strategies for the United States building sector

In this study, the impacts of various mitigation strategies for existing and newly constructed buildings in the United States on embodied and operational greenhouse gas (GHG) emissions were quantified until 2050. A bottom-up approach was utilized to model the characteristics of individual reference buildings. First, reference designs and practices were developed for climatic regions across the United States to capture spatial variation in energy demand, building codes, and structural performance. Then, the results were scaled up to regional networks (at county and state levels) and finally to the entire country. Given the fact that mitigation strategies can vary by region and building type, we explored the key drivers of impacts in the buildings sector and prioritized which strategies should be applied in different regions and building types. To meet deep decarbonization goals, we will need to pursue strategies for GHG emissions reductions in both the embodied and operational phases of the building life cycle. We found there will be no meaningful reduction in building GHG emissions in the Western US and New England regions under current projected technology and code improvements because they are on the leading edge of emissions reduction strategies. However, there is much more opportunity to lower life cycle GHG emissions in the Midwest and central US regions because they are further behind the implementation of reduction strategies. A number of interventions—chiefly to the electricity grid, appliances, and lighting—could nearly halve the emissions of new buildings constructed between 2016 and 2050.

Greenhouse gas emissions, total food spending and diet quality by share of household food spending on red meat: results from a nationally representative sample of US households.

To determine if US household food purchases with lower levels of red meat spending generate lower life-cycle greenhouse gas emissions (GHGE), greater nutritional quality and improved alignment with the Dietary Guidelines for Americans. Affordability of purchasing patterns by red meat spending levels was also assessed. Household food purchase and acquisition data were linked to an environmentally extended input-output life-cycle assessment model to calculate food GHGE. Households (n 4706) were assigned to quintiles by the share of weekly food spending on red meat. Average weekly kilojoule-adjusted GHGE, total food spending, nutrients purchased and 2010 Healthy Eating Index (HEI-2010) were evaluated using ANOVA and linear regression. USA.ParticipantsHouseholds participating in the 2012-2013 National Household Food Acquisition and Purchase Survey. There was substantial variation in the share of the household food budget spent on red meat and total spending on red meat. The association between red meat spending share and total food spending was mixed. Lower red meat spending share was mostly advantageous from a nutritional perspective. Average GHGE were significantly lower and HEI-2010 scores were significantly higher for households spending the least on red meat as a share of total food spending. Only very low levels of red meat spending as a share of total food spending had advantages for food affordability, lower GHGE, nutrients purchased and diet quality. Further studies assessing changes in GHGE and other environmental burdens, using more sophisticated analytical techniques and accounting for substitution towards non-red meat animal proteins, are needed.

Comparative life cycle assessment of biomass utilization for electricity generation in the European Union and the United States

Biomass utilization is a strategy to decrease greenhouse gas (GHG) emissions in the European Union (EU) but bioenergy in the United States (US) is currently limited. As a result, biomass is increasingly exported from the US to the EU, but changes to the policy landscape are poised to alter this. This study utilizes Life Cycle Assessment (LCA) to assess impacts of biomass transportation on bioenergy life cycle GHG emissions. Transportation modes considered include truck, train and sea freight and each are assessed at realistic distances expected in bioenergy supply chains. Emissions for biomass firing alone and co-firing with coal using wood chips and pellets are compared to a baseline coal-fired power plant. Results include life cycle emissions for each case, and sensitivity analysis is presented for variation in power plant efficiency and biomass heating value. A generalized model for estimation of bioenergy emissions is presented. In nearly all cases, biomass utilization for electricity production produces lower life cycle GHG emissions compared to the coal baseline, with emission reductions as high as 76%. Utilization in the US and EU have similar overall emissions at long US distances. Policy implications are discussed in the context of current US and EU policies.

A screening-level life cycle greenhouse gas analysis of CO2 enhanced oil recovery with CO2 sourced from the Shute Creek natural gas-processing facility

This life cycle analysis (LCA) evaluates life cycle greenhouse gas (GHG) emissions associated with a system that produces both natural gas and crude oil. Two systems are defined: System 1, which independently produces natural gas and oil, and System 2, which captures carbon dioxide (CO2) from the natural gas-processing plant and utilizes this captured CO2 for enhanced oil recovery (EOR). The LCA uses customized spreadsheet models with emission factors from peer-reviewed literature and publications of the National Energy Technology Laboratory of the U.S. Department of Energy. The modeling results show that the CO2 EOR scenario using captured CO2 produces both natural gas and oil with lower life cycle GHG emissions than alternative systems producing natural gas and oil independently. Sensitivity analyses show that the model results are most sensitive to the fraction of CO2 captured (or equivalently, the fraction of CO2 vented) at the natural gas-processing facility and the incremental oil recovery factor and net CO2 utilization factor of the EOR operations. The input variable driving the relative difference in life cycle GHG emissions between these two systems is the fraction of CO2 captured at the natural gas-processing facility (i.e., the capture rate). The results of this study highlight the necessity of linking processes in the life cycle modeling, as a change to one process can affect other processes within the coupled energy system comprised of natural gas and oil. In addition, this analysis shows, as prior work has also suggested, that CO2 EOR using captured anthropogenic CO2 provides a viable means for offsetting carbon emissions from oil production and combustion via the associated storage of CO2 that occurs incidentally during this tertiary method of oil recovery.

Life cycle analysis (LCA) of low emission methanol and di-methyl ether (DME) derived from natural gas

This paper presents an analysis of different pathways for synthesising methanol and dimethyl ether (DME) from natural gas. This work seeks to determine the conditions under which methanol and DME might simultaneously have lower lifecycle greenhouse gas emissions and lower price than gasoline and diesel. Lower lifecycle greenhouse gas emissions are found to be possible if the energy used to synthesise these fuels is from low emission sources. Both methanol and DME synthesis should also be economically competitive with these incumbent transport fuels given current clean energy prices, provided that the natural gas price is approximately at current US levels and gasoline and diesel prices are at least 0.6$US/l. This suggests that methanol and DME can be scalable, economic and environmentally preferable alternatives to gasoline and diesel, particularly in the United States.

Life cycle GHG emissions and lifetime costs of medium-duty diesel and battery electric trucks in Toronto, Canada

Battery-electric trucks (BET) are an alternative to diesel trucks and have the potential for lower life cycle greenhouse gas (GHG) emissions and total lifetime costs (TCO). This study compares a Class 6 medium-duty BET with a Class 6 medium-duty diesel truck. Vehicle fuel consumption is simulated for Toronto driving conditions, based on different drive cycles, operating temperatures and payloads. The base case results show the BET has lower life cycle GHG emissions and higher lifetime TCO than the diesel truck, but this does not hold across all conditions. GHG emissions of the BET are higher than those of the diesel truck under 100% payload in driving conditions with infrequent stops, while the results are less sensitive to operating temperature. The lifetime cost of the BET can be lower than that of the diesel truck in situations that have driving with frequent stops/starts and with low payloads and low battery and charging station costs. These variables also affect estimated GHG abatement costs, which are highly relevant as carbon pricing is being introduced in the province.

Building Energy Management Systems: Global Potentials and Environmental Implications of Deployment

SummaryOne of the key drivers that influence building energy consumption is the demand for space heating. Particularly in countries with cold climates and a large stock of residential buildings with central heating, building energy management systems (BEMS) are an option to reduce energy consumption and greenhouse gas (GHG) emissions. These systems can be combined with existing space heating technologies and other efficiency measures, such as building insulation. They are ideal for retrofitting purposes owing to their low up‐front costs. A prospective life cycle assessment model is used to analyze the environmental impacts of the technology today, in 2030, and in 2050. This allows for a first‐ever, order‐of‐magnitude assessment of the environmental impacts of BEMS over their life cycle. The assessment is based on manufacturer information and generic life cycle inventory data for electronic components. Future impacts are based on changes in electricity generation following the International Energy Agency's 2 degree and 6 degree scenarios, and are used to assess the contribution of BEMS to global energy and GHG saving goals. Results show substantially lower life cycle GHG emissions and higher savings of environmental impacts per kilowatt‐hour of heating when compared to natural gas or electric heating. Potential net emissions savings range from approximately 0.4 kilograms carbon dioxide equivalent (kg CO2‐eq) when avoiding natural gas heating to over 1 kg CO2‐eq when avoiding electric heating in regions with GHG‐intensive electricity generation. At present, BEMS can avoid at least 40 times the GHG emissions that they require for production and use, when deployed in regions with cold climates.

Life-Cycle Energy Implications of Downtown High-Rise vs. Suburban Low-Rise Living: An Overview and Quantitative Case Study for Chicago

It is commonly accepted that the concentration of people in high-density urban city centers, which are typically dominated by medium- and high-rise buildings located close to public transit systems, offers greater overall energy efficiency and lower life-cycle greenhouse gas emissions than lower-density expanded suburbs, which are dominated by low-rise single-family buildings and larger per-person automobile travel requirements. However, few studies have combined quantitative analyses of the life-cycle energy use of both buildings and transportation in both urban and suburban areas, especially in American cities. This work uses a variety of data sources to provide a quantitative comparison of the life-cycle energy consumption associated with residential life (including buildings, transportation, and supporting infrastructure) in prototypical downtown high-rises and suburban low-rises in and around Chicago, IL. We estimate that downtown high-rise living in Chicago, IL accounts for approximately 25% more life-cycle energy per person per year than suburban low-rise living, on average, contrary to some common beliefs (best estimates were ~141 and ~113 GJ/person/year, respectively). Building operational energy use was found to be the largest contributor of the total life-cycle energy in both the downtown high-rise and suburban low-rise cases, followed by vehicle operational energy.

The Green Paradox of U.S. Biofuel Subsidies: Impact on Greenhouse Gas Emissions

This paper presents the first comprehensive estimates of the impact of U.S. biofuel subsidies on greenhouse gas emissions. Although U.S. support for biofuels is large and growing, the associated impact on greenhouse gas emissions remains unclear. The effect of biofuel subsidies on emissions is determined by the relative magnitudes of countervailing substitution and price effects. Regulators typically ignore the price effect of biofuel policies, and therefore do not fully account for market and climate impacts. We develop an economic simulation model of U.S. energy markets to estimate the impact of biofuel subsidies on greenhouse gas emissions from 2005 through 2009. The model represents end-use consumption of oil, natural gas, coal and electricity in four sectors. We find that the subsidies for ethanol increased greenhouse gas emissions, while those for biodiesel have an ambiguous effect. Thus, ethanol subsidies create a green paradox. Although ethanol has lower lifecycle greenhouse gas emissions than gasoline, the subsidies lower the market price of blended fuel, which increases overall fuel consumption and increase total greenhouse gas emissions. These findings question the suitability of using ethanol subsidies to achieve climate goals and highlight the importance of accounting for the price effect of biofuel policies.

Life cycle assessment of bio-jet fuel from hydrothermal liquefaction of microalgae

Bio-jet fuel is increasingly being produced from feedstocks such as algae and tested in flight. As the industry adopts bio-jet fuels from various feedstocks and conversion processes, life cycle assessment (LCA) is necessary to determine whether these renewable fuels result in lower life cycle greenhouse gas (LC-GHG) emissions than conventional jet fuel. An LCA was performed for a functional unit of 1 GJ of bio-jet fuel produced through thermochemical conversion (hydrothermal liquefaction (HTL)) of microalgae cultivated in wastewater effluent. Two pathways were analyzed to compare the impacts of siting HTL at a wastewater treatment plant (WWTP) to those of siting HTL at a refinery. Base cases for each pathway were developed in part using primary data from algae production in wastewater effluent and HTL experiments of this algae at the University of Kansas. The LC-GHG emissions of these cases were compared to those of conventional jet fuel, and a sensitivity analysis and Monte Carlo analyses were performed. When algal conversion using HTL was modeled at a refinery versus at the WWTP site, the transportation steps of biomass and waste nutrients were major contributors to the LC-GHG emissions of algal bio-jet fuel. The LC-GHG emissions were lower for the algal bio-jet fuel pathway that performs HTL at a WWTP (35.2kg CO2eq/GJ for the base case) than for the pathway for HTL at a refinery (86.5kg CO2eq/GJ for the base case). The LCA results were particularly sensitive to the extent of heat integration, the source of the heat for HTL, and the solids content of dewatered algae. The GHG emissions of algal bio-jet fuel can be reduced by 76% compared to conventional jet fuel with feasible improvements in those sensitive parameters and siting HTL at a WWTP. Therefore, it is critical that transportation logistics, heat integration of biomass conversion processes, and nutrient supply chains be considered as investment and production of bio-jet fuels increase.

Modeling Corn Ethanol and Climate

SummaryNew fuel regulations based on life cycle greenhouse gas (GHG) emissions have focused renewed attention on life cycle models of biofuels. The BESS model estimates 25% lower life cycle GHG emissions for corn ethanol than does the well‐known GREET model, which raises questions about which model is more accurate. I develop a life cycle metamodel to compare the GREET and BESS models in detail and to explain why the results from these models diverge. I find two main reasons for the divergence: (1) BESS models a more efficient biorefinery than is modeled in the cases to which its results have been compared, and (2) in several instances BESS fails to properly count upstream emissions. Adjustments to BESS to account for these differences raise the estimated global warming intensity (not including land use change) of the corn ethanol pathway considered in that model from 45 to 61 g CO2e MJ−1. Adjusting GREET to use BESS's biorefinery performance and coproduct credit assumptions reduces the GREET estimate from 64 to 61 g CO2e MJ−1. Although this analysis explains the gap between the two models, both models would be improved with better data on corn production practices and by better treatment of agricultural inputs.

Life Cycle Assessment of Switchgrass- and Corn Stover-Derived Ethanol-Fueled Automobiles

Utilizing domestically produced cellulose-derived ethanol for the light-duty vehicle fleet can potentially improve the environmental performance and sustainability of the transport and energy sectors of the economy. A life cycle assessment model was developed to examine environmental implications of the production and use of ethanol in automobiles in Ontario, Canada. The results were compared to those of low-sulfur reformulated gasoline (RFG) in a functionally equivalent automobile. Two time frames were evaluated, one near-term (2010), which examines converting a dedicated energy crop (switchgrass) and an agricultural residue (corn stover) to ethanol; and one midterm (2020), which assumes technological improvements in the switchgrass-derived ethanol life cycle. Near-term results show that, compared to a RFG automobile, life cycle greenhouse gas (GHG) emissions are 57% lower for an E85-fueled automobile derived from switchgrass and 65% lower for ethanol from corn stover, on a grams of CO2 equivalent per kilometer basis. Corn stover ethanol exhibits slightly lower life cycle GHG emissions, primarily due to sharing emissions with grain production. Through projected improvements in crop and ethanol yields, results for the mid-term scenario show that GHG emissions could be 25-35% lower than those in 2010 and that, even with anticipated improvements in RFG automobiles, E85 automobiles could still achieve up to 70% lower GHG emissions across the life cycle.